Electric machine and method of manufacturing the same

ABSTRACT

A bearing assembly cooperates with a bearing seat formed in a bearing housing. The assembly includes a bearing having an inner ring, an outer ring and a rolling element in engagement with the inner ring and the outer ring, and an anti-rotation device. The anti-rotation device engages the outer ring of the bearing and with the bearing housing to limit the rotation of the outer ring of the bearing within the bearing seat formed in the bearing housing. The anti-rotation device includes a first feature for engagement with the outer ring of the bearing and a second feature for engagement with the bearing housing. The first feature and the second feature limit the rotation of the outer ring of the bearing within the bearing seat formed in the bearing housing

BACKGROUND OF THE INVENTION

The embodiments described herein relate generally to an electricmachine, and more specifically, to a bearing assembly with a relativemotion [bearing creep] impeding device associated with the electricmachine.

An electric machine is typically in the form of an electric generator oran electric motor. The machine typically has a centrally located shaftthat rotates relative to the machine. Electrical energy applied to coilswithin the motor initiates this relative motion which transfers thepower to the shaft and, alternatively, mechanical energy from therelative motion of the generator excites electrical energy into thecoils. For expediency the machine will be described hereinafter as amotor. It should be appreciated that a motor may operate as a generatorand vice versa.

A stationary assembly, also referred to as a stator, includes a statorcore and coils or windings positioned around portions of the statorcore. It is these coils to which energy is applied to initiate thisrelative motion which transfers the power to the shaft. These coils areformed by winding wire, typically copper, aluminum or a combinationthereof, about a central core to form the winding or coil.

The centrally located shaft supports a rotor. The rotor is thenon-stationary part of a rotary electric motor, electric generator oralternator. Motor efficiency is improved by decreasing the degree ofslip between the rotor and the stator for a given load. One way todecrease the slip is by increasing the mass of the rotor. The rotorincludes conductors, conductor bars and end-plates which transfercurrent, magnetic field and torque to the rotor and consequently torqueto the shaft.

The shaft rotatably supports the substantial weight of the rotor withinthe electric machine. At least one bearing and typically a pair ofspaced apart bearings support the shaft within a housing of the electricmachine. The bearings may be any bearing capable of supporting the loadsinvolved and of enduring the rotational speeds of the motor. Typicallymodern electric machines utilize rolling element bearings, typicallyball bearings to support the shaft and rotor. The ball bearings includean inner ring and an outer ring separated by a series of sphericalelements or balls. While the shaft is typically rigidly secured to theinner ring, the outer ring is permitted to move axial in the housing, toaccommodate various phenomenon including temperature changes, dissimilarmaterials, and tolerance stacks.

When the bearing is positioned with the shaft horizontal to the horizonor ground, a substantial radial load from the rotor is applied to thebearing. This radial load serves to inhibit relative motion or rotationof the bearing outer ring in the housing. However when the bearing ispositioned with the shaft vertical with respect to the horizon orground, radial loads can be zero or minimal, permitting relativeslippage to occur between the bearing outer ring and the housing.

The initial relative slippage is exasperated by the formation of metaldebris that forms a lapping compound between the bearing outer ring andthe housing bore. This lapping may quickly greatly enlarge the housingbore, causing excessive noise and excessive movement between the motorstator and the motor rotor, resulting in rotor/stator strike. The noiseand strike may lead to early bearing and resultant motor failure.

Many practical applications utilize motors with vertical shafts. Forexample, pumps for pools and spas and cooling fans, particularly thoseto cool air conditioning compressors. These applications are plaguedwith bearing failures caused by the relative motion of the motor bearingouter ring in the motor housing, also known as bearing creep. Typically,vertical cooling fan motors have a vertical shaft extending upwardlyfrom the motor and from which a fan is attached. The motor typically hasan upper unconstrained bearing and a lower constrained bearing. Theupper unconstrained bearing, being closer to the fan, has a greatertendency for creep, but creep can occur in any bearing application,particularly those where accommodation is made for the bearing to moveaxially with respect to its housing.

Various methods are used to limit the bearing creep. One method is toeliminate any relative motion, including axial motion, by providing aninterference fit between the bearing outer ring and the housing or byusing an adhesive between the outer ring and housing. However anysolution that eliminates all relative motion has the disadvantage of notaccommodating various phenomenon including temperature changes,dissimilar materials, and tolerance stacks that affect the relativeaxial position of the inner ring with respect to the outer ring. Such asolution may result in excessive bearing preloads and reduced bearinglife. Further, interference fit between both bearing races is notrecommended by bearing manufacturers.

Other methods, such as placing an o-ring, a polymer ring, an EC(expansion compensating bearing), between the bearing and the housingare either ineffective or not sufficiently durable. The presentinvention is directed to alleviate at least some of these problems withthe prior art.

BRIEF DESCRIPTION OF THE INVENTION

In one aspect, a bearing assembly for use in an electric machine isprovided. The assembly cooperates with a bearing seat formed in abearing housing. The assembly includes a bearing and an anti-rotationdevice. The bearing includes an inner ring, an outer ring and a rollingelement in engagement with the inner ring and the outer ring. Theanti-rotation device is adapted for engagement with the outer ring ofthe bearing and with the bearing housing to limit the rotation of theouter ring of the bearing within the bearing seat formed in the bearinghousing. The anti-rotation device includes a first feature forengagement with the outer ring of the bearing and a second feature forengagement with the bearing housing. The first feature and the secondfeature are adapted to limit the rotation of the outer ring of thebearing within the bearing seat formed in the bearing housing.

In another aspect, an anti-rotation device for use with a bearing in anelectric machine is provided. The anti-rotation device is adapted forengagement with the outer ring of the bearing and with the bearinghousing to limit the rotation of the outer ring of the bearing withinthe bearing seat formed in the bearing housing. The anti-rotation deviceincludes a first feature for engagement with the outer ring of thebearing and a second feature for engagement with the bearing housing.The first feature and the second feature are adapted to limit therotation of the outer ring of the bearing within the bearing seat formedin the bearing housing. The first feature includes an internal surfacefor engagement with the outer ring of the bearing and the second featureincludes an engagement surface for engagement with a protrusionextending from the bearing housing.

In yet another aspect, an electric machine includes a housing, a statorsecured to the housing and a rotor. The rotor is rotatable associatedwith the housing and is supported by a shaft. The machine also includesa bearing and an anti-rotation device. The bearing has an inner ring andan outer ring. The bearing is mounted in and rotatably secures the rotorto the housing. The anti-rotation device engages the outer ring of thebearing and the bearing housing to limit the rotation of the outer ringof the bearing within the bearing seat formed in the bearing housing.The anti-rotation device includes a first feature for engagement withthe outer ring of the bearing and a second feature for engagement withthe bearing housing. The first feature and the second feature limit therotation of the outer ring of the bearing within the bearing housing.The first feature includes an internal surface for engagement with theouter ring of the bearing and the second feature comprises a engagementsurface for engagement with a protrusion extending from the bearinghousing.

In yet another aspect, a method for containing a bearing in an electricmachine includes the steps of providing an anti-rotation device for usewith a bearing having an inner ring and an outer ring, engaging theanti-rotation device with the outer ring of the bearing, and engagingthe anti-rotation device with the bearing housing to limit the rotationof the outer ring of the bearing within the bearing seat formed in thebearing housing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a motor embodying the bearing assemblywith the anti-rotation device of the present invention;

FIG. 2 is a perspective view of an end cap of the motor of FIG. 1showing the bearing assembly with the anti-rotation device of thepresent invention installed into the end cap portion of the housing ofthe motor of FIG. 1;

FIG. 3 is a cross sectional view of the end cap of FIG. 2 along the line3-3 in the direction of the arrows;

FIG. 4 is an exploded perspective view of the end cap of FIG. 2 with theanti-rotation device of the present invention for use in the motor ofFIG. 1;

FIG. 5 is a perspective view of the anti-rotation device of the presentinvention;

FIG. 6 is a perspective view of the anti-rotation device of FIG. 5installed into a bearing to form the bearing assembly of the presentinvention; and

FIG. 7 is a flow chart of an exemplary method for utilizing theanti-rotation device as shown in FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

The methods, systems, and apparatus described herein provide improvedsupport for a rotor within a stator of an electric machine. Bearingsthat support the rotor in the stator need to provide for axial movementof the bearing relative to the machine housing, while inhibitingrotation of the bearing outer ring in the bearing housing. Difficultiesmay occur providing for the axial movement, while inhibiting rotation.Bearing creep may occur resulting in noise and reduced life for theelectric machine.

The methods, systems, and apparatus described herein assist in theproper support for a rotor within a stator of an electric machine. Themethods, systems, and apparatus described herein may also facilitatequieter operation and increased speed. Furthermore, the methods,systems, and apparatus described herein provide for an improved life anddurability of the motor and its appeal to the customer.

Technical effects of the methods, systems, and apparatus describedherein include at least one of improved performance and quality andreduced labor costs.

FIG. 1 is a perspective view of an exemplary electric machine 10. Whilethe machine 10 may be any electric machine including generators andmotors, typically the machine is an electric motor. The motor 10 mayhave any orientation, horizontal, vertical or otherwise. As shown themotor has a vertical orientation with the shaft extending upwardly outof the motor housing.

The electric machine 10 includes a stationary assembly 12. Electricmachine 10 also includes a machine assembly housing 18 and a rotatableassembly 22. Machine assembly housing 18 defines an interior 24 and anexterior 26 of machine 10 and is configured to at least partiallyenclose and protect stationary assembly 12 and rotatable assembly 22.Stationary assembly 12 includes a stator core 28, which includes aplurality of stator teeth or projections 30. Stator end caps arepositioned over opposed end teeth of the plurality of stator teeth 30.Wire is wound around stator teeth 30 and the stator end caps to formeach of a plurality of windings 32.

In an exemplary embodiment, stationary assembly 12 is a three phasesalient pole stator assembly. Stator core 28 is formed from a stack oflaminations made of a highly magnetically permeable material, andwindings 32 are wound on stator core 28 in a manner known to those ofordinary skill in the art. Laminations are stacked such that stator core28 reaches a predefined length 34. In the exemplary embodiment, theplurality of laminations that form the stator core 28 may be eitherinterlocked or loose laminations. In an alternative embodiment, statorcore 28 is a solid core. For example, stator core 28 may be formed froma soft magnetic composite (SMC) material, a soft magnetic alloy (SMA)material, and/or a powdered ferrite material using a sintering process.In another alternate embodiment, the windings 32 are wound around aplurality of spools (not shown), each of which is removably fitted toone of the stator teeth 30.

In one embodiment, rotatable assembly 22 includes a permanent magnetrotor core 36 and a shaft 38 and is configured to rotate around an axisof rotation 40. In the exemplary embodiment, rotor core 36 is formedfrom a stack of laminations made of a magnetically permeable materialand is substantially received in a central bore of stator core 28. WhileFIG. 1 is an illustration of a three phase electric motor, the methodsand apparatus described herein may be included within machines havingany number of phases, including single phase and multiple phase electricmachines.

In the exemplary embodiment, electric machine 10 is coupled to a fan(not shown) for moving air through an air handling system, for blowingair over cooling coils, and/or for driving a compressor within an airconditioning/refrigeration system. The shaft 38 of the machine 10extends as shown vertically upward from the machine and is used tosecure the fan to the shaft. Alternatively the electric machine may becoupled to a pump for use in pools, spas, and the like. Morespecifically, machine 10 may be used in air moving applications used inthe heating, ventilation, and air conditioning (HVAC) industry, forexample, in residential applications using ⅓ horsepower (hp) to 1 hpmotors or greater and/or in commercial and industrial applications andhermetic compressor motors used in air conditioning applications usinghigher horsepower motors, for example, but not limited to using ⅓ hp to7.5 hp motor or greater. Although described herein in the context of anair handling system, electric machine 10 may engage any suitable workcomponent and be configured to drive such a work component.Alternatively, electric machine 10 may be coupled to a power conversioncomponent, for example, an engine, a wind turbine rotor, and/or anyother component configured to rotate rotatable assembly 22 to generateelectricity using electric machine 10.

Continuing to refer to FIG. 1, the housing 18 of motor 10 includes acentral portion 42 and opposed motor end caps 44 and 46, secured tocentral portion 42 of housing 18. Bearing assemblies 48 and 50 aremounted in end caps 44 and 46, respectively and support the shaft 38 ofrotor 22 for rotation within housing 18 of motor 10. It should beappreciated that only one end cap may be used with the other end capbeing integral with the central portion of the housing.

According to the present invention, one or both of the bearingassemblies 48 and 50 include an anti-rotation device 52 according to thepresent invention. The bearing assemblies 48 and 50 support opposed endsof shaft 38. As shown bearing assembly 48 in the upper end cap 44 istypically is not captive to the cap 44 (the bearing assembly 48 isunconstrained (not contained on its lower side and can move to the downrelative to end cap 44). Conversely, the bearing assembly 50 in thelower end cap 46 is typically constrained. The shaft 38 in turn supportsa rotor, for example and as shown, permanent magnet rotor core 36.

Referring now to FIGS. 2 and 3, the bearing assembly 48 is shown ingreater detail. It should be appreciated that the bearing assembly 48and the bearing assembly 50 may be similar, and for simplificationidentical to each other. Therefore the description of bearing assembly48 may equally apply to bearing assembly 50. The bearing assembly 48includes the anti-rotation device 52 as well as bearing 54.

Referring again to FIG. 1, the bearing may be any bearing capable ofsupporting the rotor core 36. For example the bearing may be any type ofrolling element bearing. To permit operation speeds for modernelectrical machine and to provide sufficient bearing life and as shownin FIG. 3, the bearing may be a ball bearing 54. The bearing 54 includesan inner ring 56 surrounded on its outer periphery or inner race 58 byrolling elements or balls 60. A bearing ball retainer, not shown, may beused to space the balls 60 about the bearing 54. An outer ring 62surrounds balls 60 on inner periphery or outer race 64 of outer ring 62.

The inner ring 56 includes an inner surface or bore 66 to which theshaft 38 (see FIG. 1) is fitted. The shaft 38 may have any suitable fitwith the bore 66 and may be in clearance, slip fit or interference fitwith the bore 66. The shaft may be fixed to the bore of bearing by apress or interference fit or may be locked to it by adhesives or adevice, such as a bearing collar, not shown.

According to the present invention and as shown in FIGS. 2 and 3, thebearing assembly includes the anti-rotation device 52. The anti-rotationdevice 52, as shown, engages the outer ring 62 of bearing 54. The device52 may engage the outer ring 62 at any position of the device and at anyposition of the ring. As shown the device has a device bore 68 whichengages outer periphery or outside diameter 70 of outer ring 62 ofbearing 54.

As shown in FIG. 3, the upper end cap 44 is on the loaded end of themotor 10, where the outer ring 62 is not captive to the cap 44 (theouter ring 62 is not contained below or on the right of the ring 62 andcan move to the right or downwardly relative to end cap 44 as shown). Itshould be appreciated that the anti-rotation device 52 may also be usedon lower end cap 46 (see FIG. 1) which may be the non-loaded end of themotor 10. In such an application, the anti-rotation device 52 could beused as a method of capturing the outer ring of the bearing of bearingassembly 50 (see FIG. 1) from rotation within end cap and may replace orsupplement normal locking mechanisms such as clamps.

The device 52 may engage the outer ring 62 in any effective way, by abearing engagement feature or first engagement feature 72, for example,feature 72 may be in the form of providing a device (not shown) or thefeature 72 may be an adhesive, or the device and the ring may havemating features (not shown) to engage each others. As shown in FIG. 3,the feature 72 is in the form of an interference fit between device bore68 of device 52 and the outer periphery or outside diameter 70 of outerring 62 of bearing 54.

The anti-rotation device 52, as shown, also engages the motor assemblyhousing 18 (see FIG. 1) in any effective way, by a second feature ordevice engagement feature 74, for example, feature 74 may be in the formof providing a device (not shown) or, as shown, the feature 74 maycooperate with a mating feature on the housing 18 to engage each other.

As shown in greater detail in FIG. 4, the second feature or secondengagement feature 74 is in the form of a void 74 defined by anengagement surface. The engagement surface is created by making in anyway a surface below the periphery of outer diameter 70 of theanti-rotation device 52. For example the engagement surface may be inthe form of a flat on the outer periphery 70 of the anti-rotation device52. Note that the engagement surface may have any shape such as polygon,arcuate, or any irregular shape formed into outer periphery 70 of device52. The void 74 of the anti-rotation device 52 cooperates with a housingengagement feature 76 located on the assembly housing 18. The housingengagement feature 76 may be any feature that cooperates with the deviceengagement feature 74 to inhibit rotation of the device 52 in bearingouter ring 62 of bearing 54. The housing engagement feature 76 may be aseparate component or, as shown, be integral with housing 18 (or end cap44 of housing 18). The housing engagement feature 76 as shown is aprotrusion 76 that extends into void 74 of the anti-rotation device 52with the protrusion 76 engaging the flat formed on the outer periphery70 of device 52.

While the void 74 and the protrusion 76 may have any shape, forsimplicity and as shown in FIG. 4, the protrusion 76 is defined by ahousing flat 78 formed in housing bore 80 of end cap 44 of housing 18.For simplicity and to provide an effective mating feature, the void 74is defined by an anti-rotation device flat 82 formed on theanti-rotation device 52. To permit axial movement of the bearing 54 inthe end cap 44 of housing 18, outer surface 83 of anti-rotation device52 is preferably in a mating fit/clearance with housing bore 80 and theanti-rotation device flat 82 is preferably in a mating fit/clearancewith housing flat 78. The clearance of the anti-rotation device 52 withthe housing bore 80 may permit a slight relative angular movementbetween each other which may be less than 30 degrees or from 0 to 15degrees.

Referring now to FIG. 5, the anti-rotation device 52 is shown in greaterdetail. The anti-rotation device 52, as shown, is generally in the shapeof a ring defined by outer surface 83, bore 68 and opposed first andsecond faces 84 and 86, respectively. Outer edges 88 formed between thefaces 84 and 86 and outer surface 83 may be rounded, as shown, orchamfered. Likewise inner edges 90 between the faces 84 and 86 and bore68 may be rounded or chamfered, as shown.

In addition to the engagement feature 74 in the form of void 74,additional engagement features may be provided with the anti-rotationdevice 52. For example, and as shown in FIG. 5, the anti-rotation device52 may include an additional engagement feature defined by second deviceflat 92 which engages second housing flat 94 (see FIG. 4). It should beappreciated that the void may be on the housing and the protrusion maybe on the anti-rotation device.

Continuing to refer to FIG. 5, the second device flat may be similar tofirst device flat 82 and may be positioned anywhere else on the outersurface 83 of device 52. As shown and for simplicity, the second deviceflat 92 is positioned opposed to first device flat 82.

The anti-rotation device 52 may have any desired size and shape and asshown in FIG. 4, is sized to slidably fit with bore 80 of end cap 44 andto be fixedly secured to bearing outer ring 62.

Referring again to FIG. 5, the anti-rotation device 52 has a width Wbetween the first face 84 and the second face 86. The bore 68 of device52 has a diameter of DB and the device 52 has an outside diameter of DD.The flat 82 is defined by an angle Θ from centerline 40 of device 52.Width W may be the same as the width of bearing 54, as shown, or smalleror larger.

The anti-rotation device 52 may be made of any suitable durable materialor materials and may, for example be made of a metal, a polymer or acomposite material. The device may be made by and suitable process, suchas molding, casting, forming or machining, etc.

Referring now to FIG. 6, anti-rotation device 52 is shown assembled overthe bearing 54 to form bearing assembly 48.

Referring again to FIG. 4, the anti-rotation device 52, the bearing 54,are shown in an exploded position for assembly into bore 80 of end cap44 of housing 18 of motor 10. It should be appreciated that additionalcomponents may be used to complete the motor 10 of present invention.For example, as shown, a backing ring 96 may be positioned againsthousing bore face 98 of end cap 44. Further, for example and as shown awavy washer 99 may be positioned between the backing ring 96 and bearing54.

Referring now to FIG. 7, a flow chart of an exemplary method 200 forcontaining a bearing in an electric machine (see FIG. 1) is shown. Themethod 200 includes the step 202 of providing anti-rotation device 52(see FIG. 4) for use with bearing 54 having an inner ring and an outerring, the step 204 of engaging the anti-rotation device with the outerring of said bearing and the step 206 of engaging the anti-rotationdevice with the bearing housing to limit the rotation of the outer ringof said bearing within the bearing seat formed in the bearing housing.

Referring again to FIGS. 3-7, another aspect of the exemplary method 200may be in the form of the method for containing bearing 54. Theanti-rotation device 52 includes the first feature 72 for engagementwith the outer ring 62 of the bearing 54. The anti-rotation device 52also includes a second feature 74 for engagement with the bearinghousing 18. The first feature 72 and said second feature 74 are adaptedto limit the rotation of the outer ring 62 of the bearing 54 within thebearing housing 18. The first feature 72 includes an internal surface 68for engagement with the outer ring 62 of the bearing 54. The secondfeature 74 includes a void or recess 74 defined by an engagement surfacefor engagement with a protrusion 76 extending from the bearing housing18. The anti-rotation device 52 is in the form of a ring. The firstfeature 72 includes an interior surface 68 of said ring. The recess orvoid 74 is defined by a flat 82 on the exterior surface 83 of the ring.

The methods, systems, and apparatus described herein facilitateefficient and economical assembly of an electric motor. Exemplaryembodiments of methods, systems, and apparatus are described and/orillustrated herein in detail. The methods, systems, and apparatus arenot limited to the specific embodiments described herein, but rather,components of each apparatus and system, as well as steps of eachmethod, may be utilized independently and separately from othercomponents and steps described herein. Each component, and each methodstep, can also be used in combination with other components and/ormethod steps.

When introducing elements/components/etc. of the methods and apparatusdescribed and/or illustrated herein, the articles “a”, “an”, “the”, and“said” are intended to mean that there are one or more of theelement(s)/component(s)/etc. The terms “comprising”, “including”, and“having” are intended to be inclusive and mean that there may beadditional element(s)/component(s)/etc. other than the listedelement(s)/component(s)/etc.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal language of the claims.

What is claimed is:
 1. A bearing assembly for use in an electricmachine, said assembly for cooperation with a bearing seat formed in abearing housing, said assembly comprising: a bearing, said bearingincluding an inner ring, an outer ring and a rolling element inengagement with said inner ring and said outer ring; and ananti-rotation device, said anti-rotation device adapted for engagementwith the outer ring of said bearing and with the bearing housing tolimit the rotation of the outer ring of said bearing within the bearingseat formed in the bearing housing, said anti-rotation device includinga first feature for engagement with the outer ring of said bearing and asecond feature for engagement with the bearing housing, said firstfeature and said second feature adapted to limit the rotation of theouter ring of said bearing within the bearing seat formed in the bearinghousing.
 2. An assembly in accordance with claim 1: wherein said firstfeature comprises an internal surface for engagement with said outerring of said bearing; and wherein said second feature comprises anengagement surface for engagement with a protrusion extending from thebearing housing.
 3. An assembly in accordance with claim 2, where theinternal surface of said anti-rotation device has an interference fitwith said outer ring of said bearing.
 4. An assembly in accordance withclaim 1: wherein said anti-rotation device comprises a ring; whereinsaid first feature comprises an interior surface of said ring; andwherein said second feature comprises an exterior surface of said ring.5. An assembly in accordance with claim 4, wherein said second featurecomprises an engagement surface formed on the exterior surface of saidring.
 6. An assembly in accordance with claim 5, wherein the engagementsurface is defined by a flat on the exterior surface of said ring.
 7. Anassembly in accordance with claim 6, further comprising a second flat,located on the exterior surface of said ring and opposed to the firstflat.
 8. An anti-rotation device for use with a bearing in an electricmachine, said anti-rotation device adapted for engagement with the outerring of said bearing and with the bearing housing to limit the rotationof the outer ring of said bearing within the bearing seat formed in thebearing housing, said anti-rotation device including a first feature forengagement with the outer ring of said bearing and a second feature forengagement with the bearing housing, said first feature and said secondfeature adapted to limit the rotation of the outer ring of said bearingwithin the bearing seat formed in the bearing housing, said firstfeature including an internal surface for engagement with said outerring of said bearing and said second feature including a engagementsurface for engagement with a protrusion extending from the bearinghousing.
 9. An anti-rotation device in accordance with claim 8, wherethe internal surface of said anti-rotation device has an interferencefit with said outer ring of said bearing.
 10. An anti-rotation device inaccordance with claim 8: wherein said anti-rotation device comprises aring; wherein said first feature comprises an interior surface of saidring; and wherein said second feature comprises an exterior surface ofsaid ring.
 11. An anti-rotation device in accordance with claim 10,wherein said second feature comprises an engagement surface formed onthe exterior surface of said ring
 12. An anti-rotation device inaccordance with claim 11, wherein the engagement surface is defined by aflat on the exterior surface of said ring.
 13. An anti-rotation devicein accordance with claim 12, further comprising a second flat, locatedon the exterior surface of said ring and opposed to the first flat. 14.An electric machine comprising: a housing; a stator secured to saidhousing a rotor rotatable associated with said housing; a bearing havingan inner ring and an outer ring, said bearing rotatably securing saidrotor to said housing; and an anti-rotation device for use with saidbearing, said bearing mounting in housing of an electric machine, saidanti-rotation device adapted for engagement with the outer ring of saidbearing and with the bearing housing to limit the rotation of the outerring of said bearing within the bearing seat formed in the bearinghousing, wherein said anti-rotation device includes a first feature forengagement with the outer ring of the bearing and a second feature forengagement with the bearing housing, said first feature and said secondfeature adapted to limit the rotation of the outer ring of the bearingwithin the bearing housing, wherein said first feature comprises aninternal surface for engagement with said outer ring of said bearing andwherein said second feature comprises an engagement surface forengagement with a protrusion extending from the bearing housing.
 15. Anelectric machine in accordance with claim 14, where the internal surfaceof said anti-rotation device has an interference fit with said outerring of said bearing.
 16. An electric machine in accordance with claim14: wherein said anti-rotation device comprises a ring; wherein saidfirst feature comprises an interior surface of said ring; and whereinsaid second feature comprises an exterior surface of said ring.
 17. Anelectric machine in accordance with claim 16, wherein said engagementsurface is defined by a flat on the exterior surface of said ring. 18.An electric machine in accordance with claim 17: Further comprising asecond flat, located on the exterior surface of said ring and opposed tothe first flat.
 19. A method for containing a bearing in an electricmachine, comprising: providing an anti-rotation device for use with abearing having an inner ring and an outer ring; engaging theanti-rotation device with the outer ring of said bearing; and engagingthe anti-rotation device with the bearing housing to limit the rotationof the outer ring of said bearing within the bearing seat formed in thebearing housing.
 20. A method for containing a bearing in accordancewith claim 19, wherein said anti-rotation device comprises: a firstfeature for engagement with the outer ring of the bearing; and a secondfeature for engagement with the bearing housing, said first feature andsaid second feature adapted to limit the rotation of the outer ring ofthe bearing within the bearing housing, wherein said first featurecomprises an internal surface for engagement with said outer ring ofsaid bearing and wherein said second feature comprises an engagementsurface for engagement with a protrusion extending from the bearinghousing, wherein said anti-rotation device comprises a ring and whereinsaid first feature comprises an interior surface of said ring, whereinthe engagement surface is defined by a flat on the exterior surface ofsaid ring.